S.s. Sayyedain, H.r. Salimijazi, M.r. Toroghinejad, F. Karimzadeh.,
Volume 33, Issue 1 (7-2014)
Abstract
Due to their superior properties such as high specific strength, high creep resistance and high strength at elevated temperatures, aluminum composites reinforced with alumina nano particles are widely used for advanced purposes such as aerospace and auto industries. Lack of an appropriate welding process limits their applications. Transient liquid phase (TLP) bonding is one of the state-of-the-art joining processes. It is used for welding composites and advanced materials. Microstructure and mechanical properties of TLP bonding depend on the bonding time and temperature. In the current study, the effect of bonding time on the microstructure and bonding strength of the TLP diffusion bonded of Al2O3p/Al nanocomposite was investigated. A thin layer of copper deposited by electroplating was used as an interlayer. The bonding times of 20 and 40 min were not sufficient for completing the isothermal solidification, and the bonding strengths were not satisfactory. By increasing the bonding time to 60 min at constant bonding temperature of 580 ºC, the isothermal solidification was completed and the final joint microstructure consisted of soft α-Al phase with dispersed CuAl2 precipitated particles. Decreasing the amount of brittle eutectic structures in the joint seam by increasing the bonding time was the main reason for improvement of the joint shear strength. The maximum joint shear strength was achieved at 580 ºC for 60 min which was about 85% of the shear strength of the base material.
M. Jafarian, M. Paidar, M. Jafarian,
Volume 35, Issue 1 (6-2016)
Abstract
In this study, microstructure and mechanical properties of diffusion joints between 5754, 6061 and 7039 aluminum alloys and AZ31 magnesium alloy were investigated. Diffusion joints were done between the alloys at 440 °C, for duration of 60minutes, at 29 MPa pressure and under 1×10-4 torr vacuum. The interface of joints was studied using optical (OM) and scanning electron microscopy (SEM) equipped with EDS analysis and the line scan. According to the results of EDS analysis, the presence of intermetallic compounds including Al12Mg17, Al3Mg2 and their mixture was observed at the diffusion zone. Also, according to the results of the line scan, the hardness value of aluminum alloys has a considerable effect on diffusion of the magnesium atoms toward aluminum alloy and the greatest diffusion of magnesium was observed when 6061 aluminum alloy was used. More diffusion resulted in a stronger bond between atoms of magnesium and aluminum, and maximum strength of approximately 42 MPa was obtained when 6061 aluminum alloy was used.
